Study on Soil Moisture Changes in Different Years with Soil Moisture Recorder

In recent years, research on soil moisture has become more and more in-depth. Ma Zhuguo et al. studied the relationship between the characteristics of soil moisture and climate change in the eastern part of China, and studied the characteristics of soil moisture changes in Shanghai under different weather conditions. It was concluded that “10cm had the lowest soil moisture and the most intense fluctuations. The highest soil moisture in 50cm has the smallest fluctuations.

Fang Wensong et al. used a soil moisture recorder to record the annual changes in soil moisture in Henan Province and found that the soil moisture reached the lowest value in April and May, and the soil moisture reached the highest value in September and October; Wang Jianyuan et al. The soil moisture content was studied and it was concluded that the soil moisture reached the valley value in the year in June and the soil moisture reached the peak value in the year in August; Zhang Qiang et al. studied the soil hydrothermal characteristics in Dunhuang, and found that the soil moisture appeared in the region during the year. The characteristics of three highs and three lows, and the soil moisture gradually increases with depth.

Soil is a continuum of temporal and spatial variability. The moisture stored in soil is constrained by precipitation, vegetation, infiltration, and evaporation, and there are also differences in the distribution, connection, and change of space. Earth's soil moisture is an important influence factor of the ecosystem, which determines the soil evolution and land productivity. At the same time, soil moisture is the main influence factor of soil erosion process, plant growth and vegetation recovery, and it has the water-heat balance and system stability of the entire ecosystem. A decisive role.

Using the soil moisture recorder, we can find that the soil moisture is closely related to the precipitation process. The characteristics of precipitation and evaporation in an area have an important impact on the soil water cycle, but there are relatively few studies on the karst area. Therefore, to study the spatial distribution of soil moisture in karst areas and its variation in different weather backgrounds has important guiding significance for agricultural production, vegetation restoration and rational land use and allocation in karst regions.

Guizhou is located on a cascade of large slopes in the eastern part of the Yunnan-Guizhou Plateau, with 75.1% of the mountainous area, 23.6% of the hills, and only 1.3% of the plains. It is one of the typical mountainous provinces where there is no plain support in China. The terrain in the study area is rugged and steep. The terrain is fragmented and there are karst landforms with relatively well-developed remnant hills, fenglin basins, or peak forest valleys. Carbonate rocks are widely distributed, with high rock bareness. The karst area accounts for 73% of the total area. The area of ​​cultivated soil is small, mainly in zonal yellow soil and yellow-red soil. The soil distribution is sporadic and shallow, with a large proportion of rocky desertification.

In this study, the data of hourly average soil volumetric moisture measured by 12 soil moisture recorders in Guizhou were used to analyze the characteristics and laws of soil moisture changes in different weather conditions in order to explore the variability of soil moisture in Guizhou karst areas, which is a karst area. Rational use of land and water resources and ecological restoration provide scientific basis.

1. Under continuous dry weather conditions, the soil moisture content in all layers of soil decreases with the prolonged drought time. The change of surface soil moisture content is greater than that of deep soil moisture, but due to long drought and no rain, the layers Soil moisture changes in a relatively small range.

2. Under continuous dry weather conditions, there is a significant correlation between soil moisture content at all stations in most stations, but in Jiangkou, Yuping and Kaili, in the context of continuous arid weather in mid-August, soil layers The correlation between volumetric moisture content is not significant.

3. In a single rainfall process, the volume of soil moisture at the depth of 10 to 20 cm increases sharply. The deeper the soil layer, the smaller the change in water content. With the prolonged rainfall stoppage time, the volumetric soil water content at the depth of 10-20cm is significantly reduced, and the volume of soil moisture in the lower layer is steadily increased.

4. Under continuous cloudy and rainy conditions, most of the soil moisture observation stations have significant correlations between soil moisture content and rainfall at depths of 20cm and 30cm, because crop roots are distributed densely in 0-30cm soil layers, and they can absorb rainwater capacity. Stronger. The deep soil moisture content in Zhenyuan, Yuping, Tongren, and Libo has a significant correlation with rainfall, which is related to the water holding capacity of the soil texture.

The data used in this study is only the amount of precipitation and volume of soil moisture, so it is only the study of the impact of precipitation on the volume of soil moisture, and did not consider temperature, radiation, evapotranspiration and other meteorological factors, so the study has some limitations. The comprehensive effect of meteorological factors on soil moisture and the effect of different magnitude precipitation on the soil moisture in each layer have yet to be further studied.

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